Control strategy design for a SOFC-GT hybrid system equipped with anode and cathode recirculation ejectors

Abstract

The ejectors equipped for anode and cathode recirculation loops are more reliable and low-cost in maintenance than blowers in a solid oxide fuel cell-gas turbine hybrid system. However, an effective control system is one of the technical challenges associated with the development of the hybrid system. In present work, a novel control strategy was designed to restrict the hybrid system equipped with anode and cathode recirculation ejectors to a safe and feasible zone. Six control loops were carried out to control the vital parameters including power, rotation speed, fuel utilization, anode and cathode inlet temperature, and turbine inlet temperature. At the same time, the performance of another control system without anode inlet temperature control loop was also investigated. A comparison results of the two control systems reveal that both anode and cathode inlet temperature loops are necessary. If there is no anode inlet temperature control loop, the system efficiency decreases by 0.18%, the fuel cell inlet temperature differences between anode and cathode increases by 9 K and the compressor surge margin decreases by 1.8% at 95% system load. It not only causes a little reduction in efficiency but also may cause some latent dangers of the hybrid system at a part load condition. Consequently, the control system with all six control loops is effective and appropriate.